Depth Charges & Fire Barrels

[Ulzgoroth]

Originally Posted by The Colonel

The only infantry anti-pursuit mines that I've heard of being used are essentially regular mines that you lay on your back trail … although I think the US had a funky self deploying one.

Yeah, I think the M86 is what I was thinking of. It might be in High Tech?

[Siliconhobbit]

Hey everyone!

Thanks for all of the replies. I really appreciate it.

Regarding Depth Charges: For the campaign I am running (late TL4 - early ti mid TL5 Fantasy) they would definitely be used against submerged vessels and/or creatures, not for surface vessels, ships, boats, or creatures.

As for the Fire Barrels, as I had said, I had not found their particular use in the real world so their actual existence was dubious at best.

It seems as though they were created for the video game itself, for what I suspect was to add another element to ship/naval combat that could engage the player.

I would agree that they are used as an anti-pursuit "mine" in the video game specifically, with the added benefit of causing more damage and explosions than what could be produced in the real world. Again, dubious at best.

During the video game however, the Fire Barrels played 2 roles:

#1 as the anti-pursuit "mine" as one would have it. Dropped out the back of the ship into the path of the pursuing vessel to deter that pursuit. The closer to the pursuing vessel they were dropped into the water (they float by the way), the easier it was to heavily damage that vessel that was following because it could be difficult to avoid.

#2 as a blockade for ports. Some of the enemy ports had plenty of Fire Barrels floating in the bay to deter vessels from entering said bay and docking at the port. Of course, it being a video game, the barrels we're always ready to explode, should a vessel hit them, despite how long they may have been floating in the water (one was expected to suspend their belief, despite the rather ridiculous mechanic of the barrel itself).

[adm]

For what it may be worth, GURPS:WWII for 3E covers WWII depth charges, and their use, they haven't really changed in how they work since WWI, the main differences are better materials.

[johndallman]

Originally Posted by Siliconhobbit

Regarding Depth Charges: For the campaign I am running (late TL4 - early ti mid TL5 Fantasy) they would definitely be used against submerged vessels and/or creatures, not for surface vessels, ships, boats, or creatures.

In a sense, this is simple: a barrel of gunpowder with a coil of lead pipe on one end. The pipe has the fuse in it, of the kind that's cord impregnated with nitrate solution. That doesn't need an air supply, although it will go out if it gets wet.

One end of the pipe leads into the barrel, and the other end is open: you light the fuse, let it burn until the fire is definitely inside the pipe, close the open end of the pipe with pliers. and drop the barrel overboard. However, there are a lot of difficulties:

• Keeping everything watertight is the first one. That's much easier with metal than wood, but throwing away lots of metal is expensive at TL4-5.
• Making the charge sink fast enough is another. A wooden barrel, full of black powder at a density of about 1.75 grams/cubic centimetre won't sink quickly. TL6 depth charges carried substantial metal weights to help them sink.
• Getting the charge close enough to the target to do serious harm is another. You needed to be within 30 feet or so with TL6 depth charges, and it will need to be closer with lower-powered explosives. This meant that charges were usually dropped in patterns of 6-10, to cover more area, and throwing barrels around in predictable patterns without using explosives is hard.
• You need to be close in depth as well as position. The fuses aren't going to be very predictable or reliable.
• To get a chance of being close enough, you need a way of detecting your underwater targets. This was active sonar during TL6; you'll need some other way in a fantasy campaign.
• Are you dropping these from sailing ships? Large sea creatures can almost certainly simply swim away from those faster and with better manoeuvrability.

[Ulzgoroth]

Low tech depth charges are hard, but one helpful thing is that flinging depth charges around is very historical - so tossing them in the right direction with a deck-mounted catapult of some sort would be pretty appropriate. (Might be an increased risk of the barrels rupturing when they hit the water if flung rather than dumped, though.)

Originally Posted by johndallman

Getting the charge close enough to the target to do serious harm is another. You needed to be within 30 feet or so with TL6 depth charges, and it will need to be closer with lower-powered explosives. This meant that charges were usually dropped in patterns of 6-10, to cover more area, and throwing barrels around in predictable patterns without using explosives is hard.

If that's a historical number, it's presumably for attacking historical TL6 metal-hulled submarines. A TL4^/5^ submarine or an animal might be somewhat more fragile.

[dcarson]

And a animal might flee from the pain to its own echolocation organs even it it is not really damaged.

[Rupert]

Originally Posted by The Colonel

I've heard rumors that various torpedo boat forces developed a technique of running directly across the bows of a larger target and dropping a depth charge set to minimum depth so that it exploded as their opponent ran over it. I've never heard of it actually being used in combat - a few surface vessels have been sunk by depth charges, but in almost all cases, they came from the same vessel they sank.

The first effective WWI depth charge, the British Type D, had a sink rate of 7 ft/s initially, increasing to about 10 ft/s at a couple of hundred feet down. It was considered safe to use at 100+ feet by a slow (10 knot) ship, when rolled off the stern. That means it would be going off 13s after being dropped, and the ship would be at least 73 yards away. It had a 300 pound TNT warhead, so it was not a small weapon, and nor did it make a small explosion.

Thus, for a depth charge to threaten a pursuing ship, it would have to go off less than 100 feet underwater, and even if the pursuer was chasing at 30 knots, they'd need to be no more than ~200 yards behind for the charge to have any chance of damaging them.

By WWII they had twice the explosive and twice the sink rate (which actually means the pursuer needs to be faster or closer to use them), and even so had to be within about 5 yards of a submarine to sink it.

Overall, I think it's something that would be very unlikely to work.

[Fred Brackin]

Originally Posted by Ulzgoroth

Low tech depth charges are hard, but one helpful thing is that flinging depth charges around is very historical - so tossing them in the right direction with a deck-mounted catapult of some sort would be pretty appropriate. (Might be an increased risk of the barrels rupturing when they hit the water if flung rather than dumped, though.)

.

You're going to need to use fairly small barrels of gunpowder or mount the catapult on a barge being towed behind the actual ship. A 300 lb barrel of gunpowder (which would have an explosive of half the REF of Rupert's WWI depth charges) would need a full-sized trebuchet. I don't believe you could keep one of those from tangling in the rigging of a sailing ship.

[johndallman]

Originally Posted by Ulzgoroth

If that's a historical number, it's presumably for attacking historical TL6 metal-hulled submarines. A TL4^/5^ submarine or an animal might be somewhat more fragile.

It is historical. The strength of submarines largely depends on their diving depth limit. A low-tech submarine will be more fragile, as will an air-breathing animal. But a water-breather will be more robust.